This proposal deals with the role of vitamin B12 in the biosynthesis of metal-alkyls. We have now completed our studies on the biomethylation of mercury and we are working on the kinetics and mechanisms for the biomethylation of tin, selenium sulfur, and on the possible biomethylation of lead. Metal-alkyls are toxic to the central nervous system. Recently we have shown that methylmercury reacts catalytically with plasmalogens. Using 270MHz NMR, fluorescence quenching and spin labels we are trying to determine whether the reaction with plasmalogens can cause lysis of cell membranes in the central nervous system. In this study we are using lipid bilayers in addition to studying plasmalogen containing membranes in vitro and in vivo. We have purified diol dehydrase to homogeneity and we are using a fluorescent-B12-coenzyme together with substrate analogs to determine the orientation of the substrate relative to the coenzyme. We are especially interested in the distance between the corrin ring and the substrate during enzyme catalysis. Similar experiments are being performed with B12-dependent ribonucleotide reductase. We have recently shown that a good source of the latter enzyme is to be found in most species of freshwater blue-green algae. BIBLIOGRAPHIC REFERENCES: Wood, J.M., Crawford, R.L., Munck, E., Zimmermann, R., Lipscomb, J.D., Stephens, R.S., Bromley, J., Que, L. and Howard, J. The structure and function of dioxygenases: one approach to lignin degradation, ACS Meeting June 1976, San Francisco, Abstracts in Biochemistry (in press). Lipscomb, J.D., Howard, J., Lorsbach, T., and Wood, J. Protocatechuate 3,4-dioxygenase: subunit structure, Fed. Proc. (1976) (in press).